1. Field of the Invention
This invention relates to various covers for an internal combustion engine for use as an engine front cover, an oil pan and the like, and more particularly to such covers which are arranged to decrease the emission of engine noise.
2. Description of the Prior Art
Covers for moving parts of internal combustion engines, as in cylinder head covers (rocker covers), oil pans, valve lifter covers, and the like traditionally have been formed from sheet metal. Solid sheet metal is hardly a vibration or sound absorbing material; in fact, solid metal is one of the best sound and vibration conductors as well known. When a cylinder head cover or the like is rigidly mounted to an internal combustion engine, which of course, it must be in order to perform its intended function, the cover itself becomes an excellent conductor of noise and vibration produced by the internal combustion engine. In fact, due to the shape of certain types of such covers having large, essentially flat sections, these covers becomes excellent amplifiers of engine noise. Additionally, engine vibration is transmitted to the particular cover, thus creating another source of noise, i.e. the vibration of the cover itself.